Singles
Points.
The last remaining candidate in a row, column, cell, or box is called a
single. A single clears the other three sets that it occupies. A single has one
truth the can be covered by one link and is rank 0. Geometrically, a single
might be considered as a zerodimensional loop! What Sudopedia says.
Naked Single. A naked
single is the last candidate in a cell as shown in r5c5. The solid
blue square is the cell truth. The transparent bars are the three possible
links that can cover the truth.


Naked Single in 3D. A 3D
view of the same naked single. The cell truth is the short solid blue bar.
The white bars are the covering links inside the houses that see the
single. The orange cubes are the eliminated candidates.


Hidden Single. A single
candidate in a row, column, or box is a hidden single presumably because it's
harder to see. The example on the right shows a hidden single 1 in row 8.


Full House Single. The
last remaining candidate in a row, column, or a box is called a full house
single. The example on the right shows a full house single in row 3.


Single, Last Digit. A last
digit single is the last remaining candidate of a digit in the entire grid.
The grid on the right shows a last digit 7.


